This project is specifically focused on alleviating the problem of orthostatic intolerance that develops with microgravity, deconditioning and prolonged bed rest. It evaluates the mechanisms, including brain mechanisms, and couples that with an evaluation of methods of treating the problem. We approach treatment with evaluating resistance training coupled with physical countermaneuvers. The studies of the brain, and in particular, on brain stem ultra-slow rhythms detectable on amplitude modulation of the EEG, may provide important understanding of brain-stem mechanisms in regulating BP. The studies, by attempting to unify mechanism of orthostatic intolerance on earth and in space, provide a self-reinforcing approach to link space and earth. The clinical applications of the research are potentially highly significant. It may result in a new way to treat orthostatic intolerance, as well as new methods to recognize it.